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Airframe noise is a significant component of overall noise produced by transport aircraft during landing and approach (low speed maneuvers). A significant source for this noise is the cove of the leading-edge slat. The slat-cove filler (SCF) has been shown to be effective at mitigating slat noise. The objective of this work is to understand the fluid-structure interaction (FSI) behavior of a superelastic shape memory alloy (SMA) SCF in flow using both computational and physical models of a high-lift wing. Initial understanding of flow around the SCF and wing is obtained using computational fluid dynamics (CFD) analysis at various angles of attack. A framework compatible with an SMA constitutive model (implemented as a user material subroutine) is used to perform FSI analysis for multiple flow and configuration cases. A scaled physical model of the high-lift wing is constructed and tested in the Texas A&M 3 ft-by-4-foot wind tunnel. Initial validation of both CFD and FSI analysis is conducted by comparing lift, drag and pressure distributions with experimental results.

Key issues: 1) High-fidelity computational aeroelastic methods are needed to address UAV fluid/structure interaction issues; 2) These schemes will need to be very efficient to address long temporal integration requirements; 3) Well documented, basic experiments are still needed for code validation; 4) Additional disciplines may need to be added to adequately address the fluid/structure interaction issues.

Efficient modeling and computation of the nonlinear interaction of fluid with a solid undergoing nonlinear deformation has remained a challenging problem in computational science and engineering. Direct numerical simulation of the non-linear equations, governing even the most simplified fluid-structure interaction model depends on the convergence of iterative solvers which in turn relies heavily on the properties of the coupled system. The purpose of this work is to model and simulate multi-physics applications that involve fluid-structure interaction using a distributed multilevel algorithm with finite elements. The proposed algorithm is tested using COMSOL which offers the flexibility and efficiency to study coupled problems involving fluid-structure interaction. Numerical results for some benchmark fluid-structure interactions are presented that validate the proposed computational methodology for solving coupled problems involving fluid-structure interaction is reliable and robust.

The principal goals of the project are; The derivation of a uniformly stable boundary element formulations in the equations valid for the whole range of wave numbers k. The formulation should be compatible with the the C(O) regularity assumption for finite element approximations of the structure. The development of C(O) finite element approximations for one-, two-, and three- dimensional geometries. This part of the project included such fundamental issues as the development of new hp finite element data structures and constrained approximations for coupled boundary element/finite element problems. The development of a coupled finite element/boundary element code and the verification of expected rates of convergence. The derivation, implementation, and verification of an a posteriori error estimate for boundary element methods. The development of adaptive strategies. Having obtained a local error estimate, these strategies would provide for reducing mesh size or increasing spectral order so as to achieve a target error with a number of unknowns. The solution of selected problems. These are designed to demonstrate the effectiveness of the methodology on classical benchmark problems and, ultimately, on realistic scattering problems of interest in Naval research. The verification of the applicability of the hp approximation to structural mechanics, including bulky structures such as bulkheads, but also possibly shells, thin beams and plates. The development of a mathematical foundation for transient acoustics, including studying mathematical properties of linear hyperbolic systems associated with transient acoustics, the development of new transient hp-adaptive schemes, the development of high order transient solvers and associated a posteriori error estimates, and associated adaptive strategies.

This article is from Neurointervention , volume 8 . Abstract Purpose: Image-based computational models with fluid-structure interaction (FSI) can be used to perform plaque mechanical analysis in intracranial artery stenosis. We described a process in FSI study applied to symptomatic severe intracranial (M1) stenosis before and after stenting. Materials and Methods: Reconstructed 3D angiography in STL format was transferred to Magics for smoothing of vessel surface and trimming of branch vessels and to HyperMesh for generating tetra volume mesh from triangular surface-meshed 3D angiogram. Computational analysis of blood flow in the blood vessels was performed using the commercial finite element software ADINA Ver 8.5. The distribution of wall shear stress (WSS), peak velocity and pressure was analyzed before and after intracranial stenting. Results: The wall shear stress distributions from Computational fluid dynamics (CFD) simulation with rigid wall assumption as well as FSI simulation before and after stenting could be compared. The difference of WSS between rigid wall and compliant wall model both in pre- and post-stent case is only minor except at the stenosis region. These WSS values were greatly reduced after stenting to 15~20 Pa at systole and 3~5 Pa at end-diastole in CFD simulation, which are similar in FSI simulations. Conclusion: Our study revealed that FSI simulation before and after intracranial stenting was feasible despite of limited vessel wall dimension and could reveal change of WSS as well as flow velocity and wall pressure.

This article is from Journal of Biomechanics , volume 47 . Abstract Background: Compositional and morphological features of carotid atherosclerotic plaques provide complementary information to luminal stenosis in predicting clinical presentations. However, they alone cannot predict cerebrovascular risk. Mechanical stress within the plaque induced by cyclical changes in blood pressure has potential to assess plaque vulnerability. Various modeling strategies have been employed to predict stress, including 2D and 3D structure-only, 3D one-way and fully coupled fluid-structure interaction (FSI) simulations. However, differences in stress predictions using different strategies have not been assessed. Methods: Maximum principal stress (Stress-P1) within 8 human carotid atherosclerotic plaques was calculated based on geometry reconstructed from in vivo computerized tomography and high resolution, multi-sequence magnetic resonance images. Stress-P1 within the diseased region predicted by 2D and 3D structure-only, and 3D one-way FSI simulations were compared to 3D fully coupled FSI analysis. Results: Compared to 3D fully coupled FSI, 2D structure-only simulation significantly overestimated stress level (94.1 kPa [65.2, 117.3] vs. 85.5 kPa [64.4, 113.6]; median [inter-quartile range], p=0.0004). However, when slices around the bifurcation region were excluded, stresses predicted by 2D structure-only simulations showed a good correlation (R2=0.69) with values obtained from 3D fully coupled FSI analysis. 3D structure-only model produced a small yet statistically significant stress overestimation compared to 3D fully coupled FSI (86.8 kPa [66.3, 115.8] vs. 85.5 kPa [64.4, 113.6]; p

This document summarizes research done during the period June 14, 1989 through December 14, 1991 on a project aimed at the development of advanced computational methods for modeling multiscale fluid-structure interaction phenomena. The major thrust of the work reported is the development of the component parts of a new family of computational schemes that could be used to study large-scale problems in fluid-structure interaction. The overall theme of the project was the optimization of the computational process through the development of new adaptive techniques, data structures, a posteriori error estimates, and high-order solvers. The premise behind studying these types of high-order methods is that, with proper data structures, they could lead to exponential rates of convergence and thereby allow one to numerically solve very large problems, with features covering many different physical scales, using many fewer degrees of freedom than that required by conventional methods. In this spirit, the project was an ambitious one for it involved developing not only new adaptive algorithms for simulating the motion of elastic structures, but also techniques for fluid structure interaction and for modeling various regimes of incompressible viscous flows. Presumably, these methods could also be used to model the transition to turbulence and ultimately turbulent boundary layers on compliant surfaces.